Evolution… by Natural Selection 2006-2007

Why do we accept this as a Scientific Principle? What is Evolution? Evolution changes in living organisms over time explains how modern organisms have descended from ancient organisms Evolution! Evolution! Evolution! Why do we accept this as a Scientific Principle?

Biodiversity of Life on Earth Diversity of Life on Earth What do we know? There are many different creatures on Earth How do we know this? OBSERVATION Biodiversity of Life on Earth Diversity of Life on Earth What accounts for all this biological diversity? How did all these creatures come about?

What do we know? cells DNA Unity of Life on Earth All creatures have common characteristics How do we know this? OBSERVATION cells DNA Unity of Life on Earth How could all of life have the same basic features?

What do we know? Life is very old! The Earth is very old How do we know this? TESTING & OBSERVATION Radioactive Dating of the Rocks Life is very old! What’s happened to life during those billions of years?

What do we know? Creatures have changed over time How do we know this? OBSERVATION Fossil Record

What has the fossil record shown us? Many creatures that lived in the past don’t exist today OBSERVATION Origin of new species

What has the fossil record shown us? The creatures alive today haven’t always been around OBSERVATION Different species lived in the past

What has the fossil record shown us? Many creatures in the past looked like living ones we see today OBSERVATION “Family Tree” Relatives with similar, but not the same traits

Quick review, so far…. Many different species alive today All life shares common characteristics The Earth is very old Life is very old Life has changed over time The changes have been little changes over long periods of time Evolution But how does this work?

Variation What do we know? How do we know this? Populations are a mix of different individuals How do we know this? OBSERVATION Variation

What do we know? Over-production Competition Organisms have more offspring than the environment can support Not everybody survives How do we know this? OBSERVATION Over-production Competition

Over-Production & Competition How does that work? Variation Over-Production & Competition Adaptation ` Nature selects the ones that “fit” the environment better … survive & reproduce Natural Selection

What determines survival? Natural Selection traits that help individuals survive survive predators survive disease compete for food compete for territory traits that help individuals reproduce attracting a mate compete for nesting sites successfully raise young Adaptations Survival & Reproduction of the Fittest

Survival & Reproduction of the fittest not the biggest… …the fittest! not the fastest… not the bravest… not the strongest… Adaptations the traits that help an organism fit the environment better to survive & reproduce

Evolution explains Unity & Diversity Only evolution explains both unity of life similarities between all living things diversity of life wide variety of different creatures on Earth DNA

Survival & reproduction of the fittest bug…

Any Questions!! 2006-2007